Adoptive immunotherapy, which involves the transfer of autologous antigen-specific T cells generated ex vivo, is a promising strategy to treat viral infections and cancer. The T cells used for adoptive immunotherapy can be generated either by expansion of antigen-specific T cells or redirection of T cells through genetic engineering (Park, Rosenberg et al. 2011). Transfer of viral antigen specific T cells is a well-established procedure used for the treatment of transplant associated viral infections and rare viral-related malignancies. Similarly, isolation and transfer of tumor specific T cells has been shown to be successful in treating melanoma.
Novel specificities in T cells have been successfully generated through the genetic transfer of transgenic T cell receptors or chimeric antigen receptors (CARs) (Jena, Dotti et al. 2010). CARs are synthetic receptors consisting of a targeting moiety that is associated with one or more signaling domains in a single fusion molecule. In general, the binding moiety of a CAR consists of an antigen-binding domain of a single-chain antibody (scFv), comprising the light and variable fragments of a monoclonal antibody joined by a flexible linker. Binding moieties based on receptor or ligand domains have also been used successfully. The signaling domains for first generation CARs are derived from the cytoplasmic region of the CD3zeta or the Fc receptor gamma chains. First generation CARs have been shown to successfully redirect T-cell cytotoxicity. However, they failed to provide prolonged expansion and anti-tumor activity in vivo. Signaling domains from co-stimulatory molecules, as well as transmembrane and hinge domains have been added to form CARs of second and third generations, leading to some successful therapeutic trials in humans, where T-cells could be redirected against malignant cells expressing CD19 (June et al., 2011). However, the particular combination of signaling domains, transmembrane and co-stimulatory domains used with respect to CD19 ScFv, was rather antigen-specific and cannot be expanded to any antigen markers.
Multiple myeloma is a malignancy characterized by an accumulation of clonal plasma cells. Current therapies for multiple myeloma often cause remissions, but nearly all patients eventually relapse and die (Lionel S., et al. 2011). There is substantial evidence of an immune-mediated elimination of myeloma cells in the setting of allogeneic hematopoietic stem cell transplantation; however, the toxicity of this approach is high, and few patients are cured. Although some monoclonal antibodies have shown promise for treating multiple myeloma in preclinical studies and early clinical trials, consistent clinical efficacy of any monoclonal antibody therapy for multiple myeloma has not been conclusively shown (Van De Donk, N. W. C J., et al., 2012). Moreover, some monoclonal antibodies induce side effects such as hypercytokinemia, a well-known toxicity stemming from the large release of cytokines from activated immune cells. This may be observed during therapy with immune cells expressing CARs.
There is clearly a great need for new immunotherapies for multiple myeloma, and developing an effective and safe antigen-specific adoptive T-cell therapy for this disease would be a major advance
In particular, developing an effective antigen-specific adoptive T-cell therapy for such diseases inducing no or moderate hypercytokinemia would be of interest.
One candidate antigen of immunotherapies for multiple myeloma is B-cell maturation antigen (BCMA) also referred as CD269 (SwissProt/Uniprot reference Q02223). This antigen is encoded by the gene TNFRSF17. BCMA RNA was detected universally in multiple myeloma cells, and BCMA protein was detected on the surface of plasma cells from patients with multiple myeloma by several investigators (Novak A. J. et al., 2004). BCMA is a member of the TNF receptor superfamily. BCMA binds B-cell activating factor (BAFF) and a proliferation-inducing ligand (APRIL). Among nonmalignant cells, BCMA has been reported to be expressed mostly by plasma cells and subsets of mature B cells, but not by T cells and NK cells. It thus represents an appropriate target antigen for treating multiple myeloma, especially using CAR-expressing T cells.
As an alternative to the previous strategies, WO 2013/154760 proposed a BCMA CAR derived from C11 D5.3 and from C12A3.2.
As improved strategies, the present invention provides with BCMA specific CARs, which can be expressed in immune cells to target BCMA malignant cells with significant clinical advantage. In particular, the present invention provides a BCMA specific CAR, which can be expressed at the surface of immune cells, binds to BCMA and exhibit an activity towards BCMA expressing cells, in particular against BCMA expressing cancer cells, preferably said activity is a cytolytic activity against target BCMA expressing cancer cells and more preferably a cytolytic activity against target BCMA expressing cancer cells and a moderate (50% decrease) to low (70% or more decrease) expression of cytokine
There is a need to provide BCMA CARs T cells well tolerated by hosts and having the capacity to survive in the presence of drugs and target selectively BCMA expressing cells, in particular in the presence of drugs used to treat cancer, in particular cytotoxic chemotherapy agents affecting cell survival (anti-cancer chemotherapy).
Several cytotoxic agents such as anti-metabolites, alkylating agents, anthracyclines, DNA methyltransferase inhibitors, platinum compounds and spindle poisons have been developed to kill cancer cells, in particular cancer cells expressing BCMA.
These chemotherapy agents can be detrimental to the establishment of robust anti-tumor immunocompetent cells due to their non-specific toxicity. Small molecule-based therapies targeting cell proliferation pathways may also hamper the establishment of anti-tumor immunity.
Thus, there is also a need of developing well tolerated T cells targeting BCMA that would be specific and compatible with the use of drugs, in particular of anti-cancer chemotherapies, such as those affecting cell proliferation.
Thus, to use “off-the-shelf” allogeneic therapeutic cells in conjunction with chemotherapy, the inventors develop a method of engineering BCMA expressing CAR T cells that are less allogeneic, in particular cells that are less allogenic and resistant to chemotherapeutic agents and can be optionally destroyed thanks to a suicide gene.
The therapeutic benefits afforded by this strategy should be enhanced by the synergistic effects between chemotherapy and immunotherapy. Moreover, drug resistance can also benefit from the ability to selectively expand the engineered T-cell thereby avoiding the problems due to inefficient gene transfer to these cells.